This invention relates generally to techniques for sterilizing articles particularly sheet materials. More particularly, the invention relates to an apparatus and process for sterilizing materials in the form of long sheets or strips, such as packaging materials, which can be payed out from and taken up on rolls. More specifically, the invention concerns the sterilization of such sheet materials by utilizing a remarkable, heretofore unanticipated sterilization effect afforded by the combined use of H.sub.2 O.sub.2, i.e., hydrogen peroxide, and a UV, i.e., ultraviolet, lamps.
In H.sub.2 O.sub.2 sterilization as practiced heretofore, H.sub.2 O.sub.2 at room temperature has been used in some instances, but since the sterilizing or germicidal power thus obtained is weak, this technique has been inadequate for full sterilization. For this reason, heated H.sub.2 O.sub.2, which has a powerful sterilization effect, has been used in many cases.
In the use of heated H.sub.2 O.sub.2, however, steam and gaseous H.sub.2 O.sub.2 tend to leak out of the apparatus and give rise to environmental pollution, which has not been desirable for the operator.
Furthermore, since the H.sub.2 O.sub.2 thus used is in liquid form, the sterilization is of the wet type, and a large-capacity drying step has been required, which has been a difficulty in the design of the apparatus. In addition, there has also been the possibility of some H.sub.2 O.sub.2 remaining because of inadequate drying. Still another problem has been that the concentration of the H.sub.2 O.sub.2 used principally for sterilization has been 35 percent in most cases, whereby caution was necessary in handling this H.sub.2 O.sub.2.
On the other hand, sterilization of packaging materials by irradiation with a UV lamp is a dry-type sterilization, in which a drying step is unnecessary, whereby it is a simple and convenient method of great effectiveness in sterilization. However, even with the use of powerful UV lamps, a long irradiation time is required for thorough sterilization, and this long irradiation time has given rise to damaging of the packaging material, lowering of its heat-seal strength, and discoloration thereof.
Thus, these two sterilization methods, when carried out independently for thorough sterilization, have had advantages and drawbacks. There has been a need for overcoming these drawbacks.